1. Field of the Invention
The present invention relates to a three-dimensional measure device, and more particularly to a three-dimensional measure device with air bearings in which a resilient member is mounted and previously compressed.
2. Description of Related Art
A conventional three-dimensional measure device in accordance with the prior art shown in FIG. 5 comprises base member (7) and a platform (71) securely mounted on the base member (7). A bridge (72) is slidably mounted on the platform (71) and moved along a first dimension of the three-dimensional measure device. The platform (71) has a guider (711) secured on one side of the platform (71) to guide and limit the moving direction of the bridge (72). A first support (721) and a second support (722) respectively and perpendicularly connected to two opposite ends of the bridge (72) for horizontally supporting the bridge (72). The first support (721) has a free end perpendicularly slidably moved on the platform (71) and corresponding to the guider (711). The second support (722) has a free end perpendicularly slidably moved on the platform (71). The first support (721) and the second support (722) respectively correspond to two opposite sides of the platform (71). A runner (73) is slidably mounted on the bridge (72) and moved along a second dimension of the three-dimensional measure device. A tubular shaft (74) is telescopically received in the runner (73) and perpendicularly toward the platform (71). The tubular shaft (74) is moved along a third dimension of the three-dimensional measure device. A probe (75) is slightly movably received in the tubular shaft (74). Multiple air bearings (8) are mounted in the free ends of the first support (721) and the second support (722), and the runner (73) for reducing friction and measuring inaccuracy.
With reference to FIG. 6, the air bearing (8) includes a body (81) having a bottom (811) facing a plane of a comparatively moving object. A cavity (812) is defined in a top surface of body (81) and has a hemisphere shape. An outlet passage (813) is radially defined in the body (81) relative to the hemisphere cavity (812). The outlet passage (813) extends to the bottom (811) of the body (81) and communicates with the hemisphere cavity (812). A block (82) is partially received in the hemisphere cavity (812) for loading the gravity of the bridge (72)/the runner (73). The shape of the block (82) corresponds to that of the hemisphere cavity (812). An inlet passage (821) is defined in and extends through the block (82). The inlet passage (821) communicates with the outlet passage (813). A high-pressure air current flows through the inlet passage (821) and the outlet passage (813) to the bottom (811) of the body (81) such that a gap (h1) is formed between the free end of the supports (721, 722) and the platform (71) for reducing friction and easily moving the bridge (72).
The three-dimensional measure device is a very precise machine such that the gap (h1) must be controlled in a certain range with 3 μm. However, the expansion coefficients of the elements of the three-dimensional measure device are different to one another. Consequently, the temperature of the operational environment of the three-dimensional measure device is controlled about 20° C.±1° C. to prevent the three-dimensional measure device from an inaccuracy due to a change of the temperature of the operational environment and the expansion coefficients of the elements of the three-dimensional measure device. In case of power failure, the range of the gap (h1) may be changed and influence the precision of the three-dimensional measure device. For a better measure effect, the three-dimensional measure device needs to be checked when the power is supplied again. It is very inconvenient.
The present invention has arisen to mitigate and/or obviate the disadvantages of the conventional three-dimensional measure device.